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  <meta name="description" content="一、DRM核心数据结构1.1 struct drm_gem_objectlinux内核中使用struct drm_gem_object表示GEM对象，驱动一般需要用私有信息来扩展GEM对象，因此struct drm_gem_object都是嵌入在驱动私有GEM结构体内的。 创建一个GEM对象，驱动为自有GEM对象申请内存，并通过drm_gem_object_init(struct drm_devi">
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<meta property="og:description" content="一、DRM核心数据结构1.1 struct drm_gem_objectlinux内核中使用struct drm_gem_object表示GEM对象，驱动一般需要用私有信息来扩展GEM对象，因此struct drm_gem_object都是嵌入在驱动私有GEM结构体内的。 创建一个GEM对象，驱动为自有GEM对象申请内存，并通过drm_gem_object_init(struct drm_devi">
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<article id="post-rk3399/Rockchip RK3399 - DRM  gem" class="h-entry article article-type-post" itemprop="blogPost" itemscope itemtype="https://schema.org/BlogPosting">
  
    
   
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          <h3 id="一、DRM核心数据结构"><a href="#一、DRM核心数据结构" class="headerlink" title="一、DRM核心数据结构"></a>一、DRM核心数据结构</h3><h4 id="1-1-struct-drm-gem-object"><a href="#1-1-struct-drm-gem-object" class="headerlink" title="1.1 struct drm_gem_object"></a>1.1 struct drm_gem_object</h4><p>linux内核中使用struct drm_gem_object表示GEM对象，驱动一般需要用私有信息来扩展GEM对象，因此struct drm_gem_object都是嵌入在驱动私有GEM结构体内的。</p>
<p>创建一个GEM对象，驱动为自有GEM对象申请内存，并通过drm_gem_object_init(struct drm_device* ，struct drm_gem_object *，size_t )来初始化嵌入在其中的struct drm_gem_object。</p>
<p>struct drm_gem_object定义在include&#x2F;drm&#x2F;drm_gem.h:</p>
<figure class="highlight c"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span 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class="line">122</span><br><span class="line">123</span><br><span class="line">124</span><br><span class="line">125</span><br><span class="line">126</span><br><span class="line">127</span><br><span class="line">128</span><br><span class="line">129</span><br><span class="line">130</span><br><span class="line">131</span><br><span class="line">132</span><br><span class="line">133</span><br><span class="line">134</span><br><span class="line">135</span><br><span class="line">136</span><br><span class="line">137</span><br><span class="line">138</span><br><span class="line">139</span><br><span class="line">140</span><br><span class="line">141</span><br><span class="line">142</span><br><span class="line">143</span><br><span class="line">144</span><br><span class="line">145</span><br><span class="line">146</span><br><span class="line">147</span><br><span class="line">148</span><br><span class="line">149</span><br><span class="line">150</span><br><span class="line">151</span><br><span class="line">152</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/**</span></span><br><span class="line"><span class="comment"> * struct drm_gem_object - GEM buffer object</span></span><br><span class="line"><span class="comment"> *</span></span><br><span class="line"><span class="comment"> * This structure defines the generic parts for GEM buffer objects, which are</span></span><br><span class="line"><span class="comment"> * mostly around handling mmap and userspace handles.</span></span><br><span class="line"><span class="comment"> *</span></span><br><span class="line"><span class="comment"> * Buffer objects are often abbreviated to BO.</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="class"><span class="keyword">struct</span> <span class="title">drm_gem_object</span> &#123;</span></span><br><span class="line">        <span class="comment">/**</span></span><br><span class="line"><span class="comment">         * @refcount:</span></span><br><span class="line"><span class="comment">         *</span></span><br><span class="line"><span class="comment">         * Reference count of this object</span></span><br><span class="line"><span class="comment">         *</span></span><br><span class="line"><span class="comment">         * Please use drm_gem_object_get() to acquire and drm_gem_object_put_locked()</span></span><br><span class="line"><span class="comment">         * or drm_gem_object_put() to release a reference to a GEM</span></span><br><span class="line"><span class="comment">         * buffer object.</span></span><br><span class="line"><span class="comment">         */</span></span><br><span class="line">        <span class="class"><span class="keyword">struct</span> <span class="title">kref</span> <span class="title">refcount</span>;</span></span><br><span class="line"></span><br><span class="line">        <span class="comment">/**</span></span><br><span class="line"><span class="comment">         * @handle_count:</span></span><br><span class="line"><span class="comment">         *</span></span><br><span class="line"><span class="comment">         * This is the GEM file_priv handle count of this object.</span></span><br><span class="line"><span class="comment">         *</span></span><br><span class="line"><span class="comment">         * Each handle also holds a reference. Note that when the handle_count</span></span><br><span class="line"><span class="comment">         * drops to 0 any global names (e.g. the id in the flink namespace) will</span></span><br><span class="line"><span class="comment">         * be cleared.</span></span><br><span class="line"><span class="comment">         *</span></span><br><span class="line"><span class="comment">         * Protected by &amp;drm_device.object_name_lock.</span></span><br><span class="line"><span class="comment">         */</span></span><br><span class="line">        <span class="type">unsigned</span> handle_count;</span><br><span class="line"></span><br><span class="line">        <span class="comment">/**</span></span><br><span class="line"><span class="comment">         * @dev: DRM dev this object belongs to.</span></span><br><span class="line"><span class="comment">         */</span></span><br><span class="line">        <span class="class"><span class="keyword">struct</span> <span class="title">drm_device</span> *<span class="title">dev</span>;</span></span><br><span class="line"></span><br><span class="line">        <span class="comment">/**</span></span><br><span class="line"><span class="comment">         * @filp:</span></span><br><span class="line"><span class="comment">         *</span></span><br><span class="line"><span class="comment">         * SHMEM file node used as backing storage for swappable buffer objects.</span></span><br><span class="line"><span class="comment">         * GEM also supports driver private objects with driver-specific backing</span></span><br><span class="line"><span class="comment">         * storage (contiguous DMA memory, special reserved blocks). In this</span></span><br><span class="line"><span class="comment">         * case @filp is NULL.</span></span><br><span class="line"><span class="comment">         */</span></span><br><span class="line">        <span class="class"><span class="keyword">struct</span> <span class="title">file</span> *<span class="title">filp</span>;</span></span><br><span class="line">        <span class="comment">/**</span></span><br><span class="line"><span class="comment">         * @vma_node:</span></span><br><span class="line"><span class="comment">         *</span></span><br><span class="line"><span class="comment">         * Mapping info for this object to support mmap. Drivers are supposed to</span></span><br><span class="line"><span class="comment">         * allocate the mmap offset using drm_gem_create_mmap_offset(). The</span></span><br><span class="line"><span class="comment">         * offset itself can be retrieved using drm_vma_node_offset_addr().</span></span><br><span class="line"><span class="comment">         *</span></span><br><span class="line"><span class="comment">         * Memory mapping itself is handled by drm_gem_mmap(), which also checks</span></span><br><span class="line"><span class="comment">         * that userspace is allowed to access the object.</span></span><br><span class="line"><span class="comment">         */</span></span><br><span class="line">        <span class="class"><span class="keyword">struct</span> <span class="title">drm_vma_offset_node</span> <span class="title">vma_node</span>;</span></span><br><span class="line"></span><br><span class="line">        <span class="comment">/**</span></span><br><span class="line"><span class="comment">         * @size:</span></span><br><span class="line"><span class="comment">         *</span></span><br><span class="line"><span class="comment">         * Size of the object, in bytes.  Immutable over the object&#x27;s</span></span><br><span class="line"><span class="comment">         * lifetime.</span></span><br><span class="line"><span class="comment">         */</span></span><br><span class="line">        <span class="type">size_t</span> size;</span><br><span class="line"></span><br><span class="line">        <span class="comment">/**</span></span><br><span class="line"><span class="comment">         * @name:</span></span><br><span class="line"><span class="comment">         *</span></span><br><span class="line"><span class="comment">         * Global name for this object, starts at 1. 0 means unnamed.</span></span><br><span class="line"><span class="comment">         * Access is covered by &amp;drm_device.object_name_lock. This is used by</span></span><br><span class="line"><span class="comment">         * the GEM_FLINK and GEM_OPEN ioctls.</span></span><br><span class="line"><span class="comment">         */</span></span><br><span class="line">        <span class="type">int</span> name;</span><br><span class="line"></span><br><span class="line">        <span class="comment">/**</span></span><br><span class="line"><span class="comment">         * @dma_buf:</span></span><br><span class="line"><span class="comment">         *</span></span><br><span class="line"><span class="comment">         * dma-buf associated with this GEM object.</span></span><br><span class="line"><span class="comment">         *</span></span><br><span class="line"><span class="comment">         * Pointer to the dma-buf associated with this gem object (either</span></span><br><span class="line"><span class="comment">         * through importing or exporting). We break the resulting reference</span></span><br><span class="line"><span class="comment">         * loop when the last gem handle for this object is released.</span></span><br><span class="line"><span class="comment">         *</span></span><br><span class="line"><span class="comment">         * Protected by &amp;drm_device.object_name_lock.</span></span><br><span class="line"><span class="comment">         */</span></span><br><span class="line">        <span class="class"><span class="keyword">struct</span> <span class="title">dma_buf</span> *<span class="title">dma_buf</span>;</span></span><br><span class="line"></span><br><span class="line">        <span class="comment">/**</span></span><br><span class="line"><span class="comment">         * @import_attach:</span></span><br><span class="line"><span class="comment">         *</span></span><br><span class="line"><span class="comment">         * dma-buf attachment backing this object.</span></span><br><span class="line"><span class="comment">         *</span></span><br><span class="line"><span class="comment">         * Any foreign dma_buf imported as a gem object has this set to the</span></span><br><span class="line"><span class="comment">         * attachment point for the device. This is invariant over the lifetime</span></span><br><span class="line"><span class="comment">         * of a gem object.</span></span><br><span class="line"><span class="comment">         *</span></span><br><span class="line"><span class="comment">         * The &amp;drm_gem_object_funcs.free callback is responsible for</span></span><br><span class="line"><span class="comment">         * cleaning up the dma_buf attachment and references acquired at import</span></span><br><span class="line"><span class="comment">         * time.</span></span><br><span class="line"><span class="comment">         *</span></span><br><span class="line"><span class="comment">         * Note that the drm gem/prime core does not depend upon drivers setting</span></span><br><span class="line"><span class="comment">         * this field any more. So for drivers where this doesn&#x27;t make sense</span></span><br><span class="line"><span class="comment">         * (e.g. virtual devices or a displaylink behind an usb bus) they can</span></span><br><span class="line"><span class="comment">         * simply leave it as NULL.</span></span><br><span class="line"><span class="comment">         */</span></span><br><span class="line">        <span class="class"><span class="keyword">struct</span> <span class="title">dma_buf_attachment</span> *<span class="title">import_attach</span>;</span></span><br><span class="line"></span><br><span class="line">        <span class="comment">/**</span></span><br><span class="line"><span class="comment">         * @resv:</span></span><br><span class="line"><span class="comment">         *</span></span><br><span class="line"><span class="comment">         * Pointer to reservation object associated with the this GEM object.</span></span><br><span class="line"><span class="comment">         *</span></span><br><span class="line"><span class="comment">         * Normally (@resv == &amp;@_resv) except for imported GEM objects.</span></span><br><span class="line"><span class="comment">         */</span></span><br><span class="line">        <span class="class"><span class="keyword">struct</span> <span class="title">dma_resv</span> *<span class="title">resv</span>;</span></span><br><span class="line"></span><br><span class="line">        <span class="comment">/**</span></span><br><span class="line"><span class="comment">         * @_resv:</span></span><br><span class="line"><span class="comment">         *</span></span><br><span class="line"><span class="comment">         * A reservation object for this GEM object.</span></span><br><span class="line"><span class="comment">         *</span></span><br><span class="line"><span class="comment">         * This is unused for imported GEM objects.</span></span><br><span class="line"><span class="comment">         */</span></span><br><span class="line">        <span class="class"><span class="keyword">struct</span> <span class="title">dma_resv</span> _<span class="title">resv</span>;</span></span><br><span class="line"></span><br><span class="line">        <span class="comment">/**</span></span><br><span class="line"><span class="comment">         * @funcs:</span></span><br><span class="line"><span class="comment">         *</span></span><br><span class="line"><span class="comment">         * Optional GEM object functions. If this is set, it will be used instead of the</span></span><br><span class="line"><span class="comment">         * corresponding &amp;drm_driver GEM callbacks.</span></span><br><span class="line"><span class="comment">         *</span></span><br><span class="line"><span class="comment">         * New drivers should use this.</span></span><br><span class="line"><span class="comment">         *</span></span><br><span class="line"><span class="comment">         */</span></span><br><span class="line">        <span class="type">const</span> <span class="class"><span class="keyword">struct</span> <span class="title">drm_gem_object_funcs</span> *<span class="title">funcs</span>;</span></span><br><span class="line"></span><br><span class="line">        <span class="comment">/**</span></span><br><span class="line"><span class="comment">         * @lru_node:</span></span><br><span class="line"><span class="comment">         *</span></span><br><span class="line"><span class="comment">         * List node in a &amp;drm_gem_lru.</span></span><br><span class="line"><span class="comment">         */</span></span><br><span class="line">        <span class="class"><span class="keyword">struct</span> <span class="title">list_head</span> <span class="title">lru_node</span>;</span></span><br><span class="line"></span><br><span class="line">        <span class="comment">/**</span></span><br><span class="line"><span class="comment">         * @lru:</span></span><br><span class="line"><span class="comment">         *</span></span><br><span class="line"><span class="comment">         * The current LRU list that the GEM object is on.</span></span><br><span class="line"><span class="comment">         */</span></span><br><span class="line">        <span class="class"><span class="keyword">struct</span> <span class="title">drm_gem_lru</span> *<span class="title">lru</span>;</span></span><br><span class="line">&#125;;</span><br></pre></td></tr></table></figure>

<p><strong>参考文章</strong></p>
<p><strong>[1] <a target="_blank" rel="noopener" href="https://blog.csdn.net/ytfy339784578/article/details/104557569">DRM的GEM</a></strong></p>

        
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